Attack on Private Signature Keys of the OpenPGP Format, PGP(TM) Programs and Other Applications Compatible with OpenPGP

The article describes an attack on OpenPGP format, which leads to disclosure of the private signature keys of the DSA and RSA algorithms. The OpenPGP format is used in a number of applications including PGP, GNU Privacy Guard and other programs specified on the list of products compatible with OpenPGP, which is available at http://www.pgpi.org/products. Therefore all these applications must undergo the same revision as the actual program PGP. The success of the attack was practically verified and demonstrated on the PGP program, version 7.0.3 with a combination of AES and DH/DSS algorithms. As the private signature key is the basic information of the whole system which is kept secret, it is encrypted using the strong cipher. However, it shows that this protection is illusory, as the attacker has neither to attack this cipher nor user´s secret passphrase. A modification of the private key file in a certain manner and subsequent capturing of one signed message is sufficient for successful attack. Insufficient protection of the integrity of the public as well as private parts of signature keys in the OpenPGP format is analyzed in DSA and RSA algorithms and on the basis of this, a procedure of attacks is shown on both private signature keys. The attacks apply to all lengths of parameters (modules, keys) of RSA and DSA. In the end the cryptographic measures for correction of the OpenPGP format as well as PGP format are proposed

Implementação eficiente em software de criptossistemas de curvas elipticas

Orientador: Ricardo DahabTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: A criptografia de chave-pública é, reconhecidamente, uma ferramenta muito útil para prover requisitos de segurança tais como confidencialidade, integridade, autenticidade e não-repudio, parte integrante das comunicações. A principal vantagem dos criptossistemas de curvas elípticas (CCE) em relação a outras tecnologias de chave-pública concorrentes tais como RSA e DSA, é que parâmetros significativamente menores podem ser usados nos CCE com o mesmo nível de segurança. Essa vantagem é especialmente importante em aplicações em ambientes computacionais limitados como cartões inteligentes, telefones celulares, computadores de bolso e pagers. De um ponto de vista prático, a implementação dos CCE apresenta vários desafios. Uma aplicação baseada nos CCE precisa que várias escolhas sejam feitas tais como o nível de segurança, algoritmos para implementar a aritmética no corpo finito subjacente, algoritmos para implementar a aritmética na curva elíptica, protocolos de curvas elípticas e a plataforma computacional. Essas escolhas podem ter um grande impacto no desempenho da aplicação resultante. Esta dissertação trata do desenvolvimento de algoritmos eficientes para implementação em software de criptossistemas de curvas elípticas sobre o corpo finito F2m. Neste contexto, foram desenvolvidos métodos eficientes para implementar a aritmética no corpo finito F2m, e para calcular múltiplos de um ponto elíptico, a operação fundamental da criptografia pública baseada em curvas elípticas. Nesta dissertação também foi abordado o problema da implementação eficiente em software dos algoritmos propostos, em diferentes plataformas computacionais tais como PCs, estações de trabalho, e em dispositivos limitados como o pager da RIM.Abstract: It is widely recognized that public-key cryptography is an important tool for providing security services such as confidentiality, data integrity, authentication and non-repudiation, which are requirements present in almost all communications. The main advantage of elliptic curve cryptography (ECC) over competing public-key technologies such as RSA and DSA is that significantly smaller parameters can be used in ECC, but with equivalent levels of security. This advantage is especially important for applications on constrained environments such as smart cards, cell phones, personal device assistants, and pagers. From a practical point of view, the implementation of ECC presents various challenges. An ECC-based application requires that several choices be made including the security level, algorithms for implementing the finite field arithmetic, algorithms for implementing the elliptic group operation, elliptic curve protocols, and the computer platform. These choices may have a significant impact on the performance of the resulting application. This dissertation focuses on developing efficient algorithms for software implementation of ECC over F2m. In this framework, we study different ways of efficiently implementing arithmetic in F2¿, and computing an elliptic scalar multiplication, the central operation of public-key cryptography based on elliptic curves. We also concentrate on the software implementation of these algorithms for different platforms including PCs, workstations, and constrained devices such as the RIM interactive pager. This dissertation is a collection of five papers written in English, with an introduction and conclusions written in Portuguese.DoutoradoDoutor em Ciência da Computaçã

Caveat Implementor! Key Recovery Attacks on MEGA

MEGA is a large-scale cloud storage and communication platform that aims to provide end-to-end encryption for stored data. A recent analysis by Backendal, Haller and Paterson (IEEE S&P 2023) invalidated these security claims by presenting practical attacks against MEGA that could be mounted by the MEGA service provider. In response, the MEGA developers added lightweight sanity checks on the user RSA private keys used in MEGA, sufficient to prevent the previous attacks. We analyse these new sanity checks and show how they themselves can be exploited to mount novel attacks on MEGA that recover a target user’s RSA private key with only slightly higher attack complexity than the original attacks. We identify the presence of an ECB encryption oracle under a target user’s master key in the MEGA system; this oracle provides our adversary with the ability to partially overwrite a target user’s RSA private key with chosen data, a powerful capability that we use in our attacks. We then present two distinct types of attack, each type exploiting different error conditions arising in the sanity checks and in subsequent cryptographic processing during MEGA’s user authentication procedure. The first type appears to be novel and exploits the manner in which the MEGA code handles modular inversion when recomputing u = q−1 mod p. The second can be viewed as a small subgroup attack (van Oorschot and Wiener, EUROCRYPT 1996, Lim and Lee, CRYPTO 1998). We prototype the attacks and show that they work in practice. As a side contribution, we show how to improve the RSA key recovery attack of Backendal-Haller-Paterson against the unpatched version of MEGA to require only 2 logins instead of the original 512. We conclude by discussing wider lessons about secure implementation of cryptography that our work surfaces.ISSN:0302-9743ISSN:1611-334

MEGA: Malleable Encryption Goes Awry

MEGA is a leading cloud storage platform with more than 250 million users and 1000 Petabytes of stored data. MEGA claims to offer user-controlled, end-to-end security. This is achieved by having all data encryption and decryption operations done on MEGA clients, under the control of keys that are only available to those clients. This is intended to protect MEGA users from attacks by MEGA itself, or by adversaries who have taken control of MEGA’s infrastructure. We provide a detailed analysis of MEGA’s use of cryptography in such a malicious server setting. We present five distinct attacks against MEGA, which together allow for a full compromise of the confidentiality of user files. Additionally, the integrity of user data is damaged to the extent that an attacker can insert malicious files of their choice which pass all authenticity checks of the client. We built proof-of-concept versions of all the attacks. Four of the five attacks are eminently practical. They have all been responsibly disclosed to MEGA and remediation is underway. Taken together, our attacks highlight significant shortcomings in MEGA’s cryptographic architecture. We present immediately deployable countermeasures, as well as longer-term recommendations. We also provide a broader discussion of the challenges of cryptographic deployment at massive scale under strong threat models

Design principles and patterns for computer systems that are simultaneously secure and usable

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 429-464) and index.It is widely believed that security and usability are two antagonistic goals in system design. This thesis argues that there are many instances in which security and usability can be synergistically improved by revising the way that specific functionality is implemented in many of today's operating systems and applications. Specific design principles and patterns are presented that can accomplish this goal. Patterns are presented that minimize the release of confidential information through remnant and remanent data left on hard drives, in web browsers, and in documents. These patterns are based on a study involving the purchase of 236 hard drives on the secondary market, interviews conducted with organizations whose drives had been acquired, and through a detailed examination of modern web browsers and reports of information leakage in documents. Patterns are presented that enable secure messaging through the adoption of new key management techniques. These patterns are supported through an analysis of S/MIME handling in modern email clients, a survey of 469 Amazon.com merchants, and a user study of 43 individuals. Patterns are presented for promoting secure operation and for reducing the danger of covert monitoring. These patterns are supported by the literature review and an analysis of current systems.(cont.) In every case considered, it is shown that the perceived antagonism of security and usability can be scaled back or eliminated by revising the underlying designs on which modern systems are conceived. In many cases these designs can be implemented without significant user interface changes. The patterns described in this thesis can be directly applied by today's software developers and used for educating the next generation of programmers so that longstanding usability problems in computer security can at last be addressed. It is very likely that additional patterns can be identified in other related areas.by Simson L. Garfinkel.Ph.D

Caveat Implementor! Key Recovery Attacks on MEGA

MEGA is a large-scale cloud storage and communication platform that aims to provide end-to-end encryption for stored data. A recent analysis by Backendal, Haller and Paterson (IEEE S&P 2023) invalidated these security claims by presenting practical attacks against MEGA that could be mounted by the MEGA service provider. In response, the MEGA developers added lightweight sanity checks on the user RSA private keys used in MEGA, sufficient to prevent the previous attacks. We analyse these new sanity checks and show how they themselves can be exploited to mount novel attacks on MEGA that recover a target user\u27s RSA private key with only slightly higher attack complexity than the original attacks. We identify the presence of an ECB encryption oracle under a target user\u27s master key in the MEGA system; this oracle provides our adversary with the ability to partially overwrite a target user\u27s RSA private key with chosen data, a powerful capability that we use in our attacks. We then present two distinct types of attack, each type exploiting different error conditions arising in the sanity checks and in subsequent cryptographic processing during MEGA\u27s user authentication procedure. The first type appears to be novel and exploits the manner in which the MEGA code handles modular inversion when recomputing $u = q^{-1} \bmod p$. The second can be viewed as a small subgroup attack (van Oorschot and Wiener, EUROCRYPT 1996, Lim and Lee, CRYPTO 1998). We prototype the attacks and show that they work in practice. As a side contribution, we show how to improve the RSA key recovery attack of Backendal-Haller-Paterson against the unpatched version of MEGA to require only 2 logins instead of the original 512. We conclude by discussing wider lessons about secure implementation of cryptography that our work surfaces

The development of a model to effectively utilise computer mediated communication to support assessment in a virtual learning environment

Programming lecturers are faced with logistical problems associated with evaluating students’ assignments. This dissertation will discuss the problems associated with paper- and electronic-based submission and evaluation systems. Managing student assignments is thus an important issue and this dissertation investigates how the computer can be used to help in both the management of programming assignments and giving of feedback for those assignments. Computer Mediated Communication (CMC) technologies offer a technical solution for the submission of assignments. CMC technologies are therefore studied and their use in the educational sphere discussed. Information Security is another important feature that is needed when using CMC for assignment management. A guideline showing the different features that an assignment management and feedback system would need was developed. Current systems that offer some assignment management features were studied and evaluated according to the guideline. A model was developed for the management of programming assignments. The model addresses the problems of paper-based and previous electronic submission systems and includes the assessment of the assignments. The viability of the model was determined by building and testing a prototype based on the model’s specifications. The prototype was evaluated within a second year Visual Basic programming class. The evaluation determined that there were areas that needed improvement, however the feedback was generally positive

Supporting NAT traversal and secure communications in a protocol implementation framework

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresThe DOORS framework is a versatile, lightweight message-based framework developed in ANSI C++. It builds upon research experience and subsequent knowledge garnered from the use and development of CVOPS and OVOPS, two well known protocol development frameworks that have obtained widespread acceptance and use in both the Finnish industry and academia. It conceptually resides between the operating system and the application, and provides a uniform development environment shielding the developer from operating system speci c issues. It can be used for developing network services, ranging from simple socket-based systems, to protocol implementations, to CORBA-based applications and object-based gateways. Originally, DOORS was conceived as a natural extension from the OVOPS framework to support generic event-based, distributed and client-server network applications. However, DOORS since then has evolved as a platform-level middleware solution for researching the provision of converged services to both packet-based and telecommunications networks, enterprise-level integration and interoperability in future networks, as well as studying application development, multi-casting and service discovery protocols in heterogeneous IPv6 networks. In this thesis, two aspects of development work with DOORS take place. The rst is the investigation of the Network Address Translation (NAT) traversal problem to give support to applications in the DOORS framework that are residing in private IP networks to interwork with those in public IP networks. For this matter this rst part focuses on the development of a client in the DOORS framework for the Session Traversal Utilities for NAT (STUN) protocol, to be used for IP communications behind a NAT. The second aspect involves secure communications. Application protocols in communication networks are easily intercepted and need security in various layers. For this matter the second part focuses on the investigation and development of a technique in the DOORS framework to support the Transport Layer Security (TLS) protocol, giving the ability to application protocols to rely on secure transport layer services